The present invention concerns a static pick-up for a timepiece comprising at least two juxtaposed touch sensitive capacitive electrodes arranged to be manually activated and electronic means arranged and adapted to detect each position of the finger which corresponds to at least one symbol in the form of a digit, a letter or special sign.
Capacitive static pick-ups are known from the state of the art. In certain applications they may advantageously replace mechanical pushbuttons and may be found for example in control systems for lifts, in programming of sewing machines, and for controlling various functions of an electronic timepiece, such as time setting or the choice of a precise function.
In the case of utilisation of such a pick-up in timekeeping, one may readily understand the interest that this exhibits over a mechanical pushbutton which must pass through a casing in order to be accessible from the exterior and which from this fact causes problems of sealing and contamination thereby bringing about an increase in manufacturing costs and a lessening of the reliability of the control system. It must also be mentioned that the space occupied by a static pick-up may be reduced to dimensions substantially less than those of a traditional mechanical pushbutton.
In U.S. patent application Ser. No. 217,079 filed Dec. 16, 1980, the applicant has proposed a data entry device for a timepiece comprising a static pick-up formed by the juxtaposition of N electrodes providing at the output at least N-l coded information signals representing the position of the finger on the pick-up characterized by the fact that it comprises means for generating signals representing the data which one seeks to select or to modify, means for displaying symbols on a composite display and means for detecting the sense and the speed of movement of the finger over the pick-up. If the application cited describes in detail the electronic arrangement of such a device, nothing therein relates to the practical realisation of the sensing keys and the matter by which these may be incorporated into the timepiece.
The purpose of the present invention is to propose an original design comprising the juxtaposition of at least two electrodes such as may satisfy the requirements for proper functioning of the data entry device of the cited application.
A further purpose of the invention is to provide a compact device which is readily mass produced, having reduced dimensions which incorporates not only the capacitive keys, but further the electronic circuit which assures its operation.
Still a further purpose of the invention is to realise a sensitive pick-up having a decorative aspect, water-tight and especially resistant to mechanical, physical and chemical stresses which may be found in the usual environment of a wrist-watch.
These purposes may be obtained through use of the claimed means.